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🔗 Most Livable Cities
The world's most livable cities is an informal name given to any list of cities as they rank on an annual survey of living conditions. In addition to providing clean water, clean air, adequate food and shelter, a ‘livable’ city must also generate a sense of community and offer hospitable settings for all, especially young people, to develop social skills, a sense of autonomy and identity.
Regions with cities commonly ranked in the top 50 include Australia, New Zealand, Canada and Europe. Three examples of such surveys are Monocle's "Most Liveable Cities Index", the Economist Intelligence Unit's "Global Liveability Ranking", and "Mercer Quality of Living Survey". Numbeo has the largest statistics and survey data based on cities and countries. Deutsche Bank's Liveability Survey is another ranking of cities by quality of life.
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- "Most Livable Cities" | 2021-07-25 | 16 Upvotes 8 Comments
🔗 Yo-yo problem
In software development, the yo-yo problem is an anti-pattern that occurs when a programmer has to read and understand a program whose inheritance graph is so long and complicated that the programmer has to keep flipping between many different class definitions in order to follow the control flow of the program. It often happens in object-oriented programming. The term comes from comparing the bouncing attention of the programmer to the up-down movement of a toy yo-yo. Taenzer, Ganti, and Podar described the problem by name, explaining: "Often we get the feeling of riding a yoyo when we try to understand one of these message trees."
Most practices of object-oriented programming recommend keeping the inheritance graph as shallow as possible, in part to avoid this problem. The use of composition instead of inheritance is also strongly preferred, although this still requires that a programmer keep multiple class definitions in mind at once.
More generally, the yo-yo problem can also refer to any situation where a person must keep flipping between different sources of information in order to understand a concept.
Object-oriented design techniques such as documenting layers of the inheritance hierarchy can reduce the effect of this problem, as they collect in one place the information that the programmer is required to understand.
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- "Yo-yo problem" | 2014-06-26 | 10 Upvotes 2 Comments
🔗 Helium Flash
A helium flash is a very brief thermal runaway nuclear fusion of large quantities of helium into carbon through the triple-alpha process in the core of low mass stars (between 0.8 solar masses (M☉) and 2.0 M☉) during their red giant phase. The Sun is predicted to experience a flash 1.2 billion years after it leaves the main sequence. A much rarer runaway helium fusion process can also occur on the surface of accreting white dwarf stars.
Low-mass stars do not produce enough gravitational pressure to initiate normal helium fusion. As the hydrogen in the core is exhausted, some of the helium left behind is instead compacted into degenerate matter, supported against gravitational collapse by quantum mechanical pressure rather than thermal pressure. Subsequent hydrogen shell fusion further increases the mass of the core until it reaches temperature of approximately 100 million kelvin, which is hot enough to initiate helium fusion (or "helium burning") in the core.
However, a fundamental quality of degenerate matter is that increases in temperature do not produce an increase in the pressure of the matter until the thermal pressure becomes so very high that it exceeds degeneracy pressure. In main sequence stars, thermal expansion regulates the core temperature, but in degenerate cores, this does not occur. Helium fusion increases the temperature, which increases the fusion rate, which further increases the temperature in a runaway reaction which quickly spans the entire core. This produces a flash of very intense helium fusion that lasts only a few minutes, but during that time, produces energy at a rate comparable to the entire Milky Way galaxy.
In the case of normal low-mass stars, the vast energy release causes much of the core to come out of degeneracy, allowing it to thermally expand. This consumes most of the total energy released by the helium flash, and any left-over energy is absorbed into the star's upper layers. Thus the helium flash is mostly undetectable by observation, and is described solely by astrophysical models. After the core's expansion and cooling, the star's surface rapidly cools and contracts in as little as 10,000 years until it is roughly 2% of its former radius and luminosity. It is estimated that the electron-degenerate helium core weighs about 40% of the star mass and that 6% of the core is converted into carbon.
🔗 Floyd–Hoare logic
Hoare logic (also known as Floyd–Hoare logic or Hoare rules) is a formal system with a set of logical rules for reasoning rigorously about the correctness of computer programs. It was proposed in 1969 by the British computer scientist and logician Tony Hoare, and subsequently refined by Hoare and other researchers. The original ideas were seeded by the work of Robert W. Floyd, who had published a similar system for flowcharts.
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- "Floyd–Hoare logic" | 2015-07-13 | 36 Upvotes 14 Comments
🔗 Taumatawhakatangihangakoauauotamateaturipukakapikimaungahoronukupokaiwhenuaki
Taumatawhakatangihangakoauauotamateaturipukakapikimaungahoronukupokaiwhenuakitanatahu is a hill near Porangahau, south of Waipukurau in southern Hawke's Bay, New Zealand. The height of the hill is 305 metres (1,001 ft). The hill is notable primarily for its unusually long name, which is of Māori origin; it is often shortened to Taumata for brevity. It has gained a measure of fame as it is the longest place name found in any English-speaking country, and possibly the longest place name in the world; according to World Atlas. The name of the hill (with 85 characters) has also been listed in the Guinness World Records as the longest place name. Other versions of the name, including longer ones, are also sometimes used.
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- "Taumatawhakatangihangakoauauotamateaturipukakapikimaungahoronukupokaiwhenuak" | 2020-08-06 | 19 Upvotes 4 Comments
- "Taumatawhakatangihangakoauauotamateaturipukakapikimaungahoronukupokaiwhenuaki" | 2018-07-12 | 26 Upvotes 17 Comments
🔗 The Begum's Fortune
The Begum's Fortune (French: Les Cinq cents millions de la Bégum, literally "the 500 millions of the begum"), also published as The Begum's Millions, is an 1879 novel by Jules Verne, with some utopian elements and other elements that seem clearly dystopian. It is noteworthy as the first published book in which Verne was cautionary, and somewhat pessimistic about the development of science and technology.
Long after The Begum's Fortune was published, it came out that its story is based on a manuscript by Paschal Grousset, a Corsican revolutionary who had participated in the Paris Commune and was at the time living in exile in the United States and London. It was bought by Pierre-Jules Hetzel, the publisher of most of Verne's books. The attribution of plot elements between Grousset's original text and Verne's work on it has not been completely defined. Later, Verne worked similarly on two more books by Grousset and published them under his name, before the revolutionary finally got a pardon and was able to return to France and resume publication in his own name.
The book first appeared in a hasty and poorly done English translation soon after its publication in French—one of the bad translations considered to have damaged Verne's reputation in the English-speaking world. W. H. G. Kingston was near death and deeply in debt at the time. His wife, Mrs. A. K. Kingston, who did the translation for him, was certainly otherwise preoccupied than with the accuracy of the text and may have had to rely on outside help. In 2005 a new translation from the French was made by Stanford Luce and published by Wesleyan University.
I. O. Evans, in his introduction to his "Fitzroy Edition" of The Begum's Fortune, suggested a connection between the creation of artificial satellites in this novel and the publication of The Brick Moon by Edward Everett Hale in 1869.
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- "The Begum's Fortune" | 2021-08-25 | 36 Upvotes 11 Comments
🔗 Dry Water
Dry water , an unusual form of "powdered liquid", is a water–air emulsion in which tiny water droplets, each the size of a grain of sand, are surrounded by a sandy silica coating. Dry water actually consists of 95% liquid water, but the silica coating prevents the water droplets from combining and turning back into a bulk liquid. The result is a white powder that looks very similar to table salt. It is also more commonly known among researchers as empty water.
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- "Dry Water" | 2018-09-11 | 543 Upvotes 180 Comments
- "Dry water" | 2016-08-26 | 13 Upvotes 1 Comments
🔗 Wiio’s laws: Communication usually fails, except by accident
Wiio's laws are humoristically formulated observations about how humans communicate.
Wiio's laws are usually summarized with "Human communications usually fail except by accident", which is the main observation made by Professor Osmo Antero Wiio in 1978.
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- "Wiio’s laws: Communication usually fails, except by accident" | 2023-07-20 | 33 Upvotes 5 Comments
🔗 Dry Cask Storage
Dry cask storage is a method of storing high-level radioactive waste, such as spent nuclear fuel that has already been cooled in a spent fuel pool for at least one year and often as much as ten years. Casks are typically steel cylinders that are either welded or bolted closed. The fuel rods inside are surrounded by inert gas. Ideally, the steel cylinder provides leak-tight containment of the spent fuel. Each cylinder is surrounded by additional steel, concrete, or other material to provide radiation shielding to workers and members of the public.
There are various dry storage cask system designs. With some designs, the steel cylinders containing the fuel are placed vertically in a concrete vault; other designs orient the cylinders horizontally. The concrete vaults provide the radiation shielding. Other cask designs orient the steel cylinder vertically on a concrete pad at a dry cask storage site and use both metal and concrete outer cylinders for radiation shielding. Until 2024/25, there was no long term permanent storage facility anywhere in the world, and most countries still don't have a facility; dry cask storage is designed as an interim safer solution than spent fuel pool storage.
Some of the cask designs can be used for both storage and transportation. Three companies – Holtec International, NAC International and Areva-Transnuclear NUHOMS – are marketing Independent Spent Fuel Storage Installations (ISFSI) based upon an unshielded multi-purpose canister which is transported and stored in on-site vertical or horizontal shielded storage modules constructed of steel and concrete.
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- "Dry Cask Storage" | 2024-09-20 | 11 Upvotes 21 Comments
🔗 ZMODEM
ZMODEM is a file transfer protocol developed by Chuck Forsberg in 1986, in a project funded by Telenet in order to improve file transfers on their X.25 network. In addition to dramatically improved performance compared to older protocols, ZMODEM also offered restartable transfers, auto-start by the sender, an expanded 32-bit CRC, and control character quoting supporting 8-bit clean transfers, allowing it to be used on networks that would not pass control characters.
In contrast to most transfer protocols developed for bulletin board systems (BBSs), ZMODEM was not directly based on, nor compatible with, the seminal XMODEM. Many variants of XMODEM had been developed in order to address one or more of its shortcomings, and most remained backward compatible and would successfully complete transfers with "classic" XMODEM implementations.
ZMODEM eschewed backward compatibility in favor of producing a radically improved protocol. It performed as well or better than any of the high-performance varieties of XMODEM, did so over links that previously didn't work at all, like X.25, or had poor performance, like Telebit modems, and included useful features found in few or no other protocols. ZMODEM became extremely popular on bulletin board systems (BBS) in the early 1990s, becoming a standard as widespread as XMODEM had been before it.
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- "ZMODEM" | 2016-10-22 | 132 Upvotes 99 Comments